Cave of the Mounds, a natural limestone cave located near Blue Mounds, Wisconsin, United States, is named for two nearby hills called the Blue Mounds. It is located in the southern slope of the east hill. The cave's beauty comes from its many varieties of mineral formations called speleothems. The Chicago Academy of Sciences considers the Cave of the Mounds to be "the significant cave of the upper Midwest" because of its beauty, and it is promoted as the "jewel box" of major American caves.

History

The limestone from which the cave was carved began forming approximately 488 million years ago, during the Ordovician Period. During this time, much of North America was covered with warm, shallow seas. Over millions of years, calcium carbonate shells from tiny marine organisms accumulated on the sea floor, forming enormous quantities of limestone. The type of limestone in which the cave was formed is called galena dolomite because of its high concentration of the lead ore galena.

The cave began forming about a million to a million and a half years ago, Since then, the wooden walkways have been replaced with concrete ones to accommodate the many visitors. Theatrical lighting, original design by Gilbert Vaughn Hemsley Jr. has also been installed to further highlight the colors and shapes inside the cave. In 1987, the cave was designated a National Natural Landmark by the United States Department of the Interior and the National Park Service. To be considered a NNL, "a site must be one of the best examples of a natural region's characteristic biotic or geologic features."

Formations

Cave of the Mounds is home to many varieties of speleothems. As with most caves, stalactites and stalagmites are common. Formations found inside the cave include:

  • Soda straws – Soda straws are formations characterized by thin, hollow tubes made of minerals. They have the potential to form into stalactites if the holes at the bottom of them become plugged.
  • Flowstones – Flowstones are created when water travels along a surface and deposits minerals. In limestone caves, flowstones are generally the most common type of formation.
  • Curtains – These are formed when water droplets run along the ceiling of the cave and gradually form sheets of minerals.
  • Lily pads – Lily pads are created when water droplets fall into a puddle and create a formation on the surface reminiscent of a lily pad.
  • Helictites – Helictites are an unusual form of stalactite that grow with bends or angles in them that seem to defy gravity. Their strange growth style is most likely caused by capillary forces acting on the water droplets.
  • Oolites – Also called "cave pearls", they are a beautiful but rare speleothem. These are spherical formations made when a droplet falls onto some sand and calcite forms around the sand, much like the way a pearl is formed.

These formations come in many different brilliant colors such as reds, browns, blues, and grays. The reds and browns are caused by the presence of iron oxide in the formation. Similarly, blues and grays are caused by manganese oxide. Some speleothems are even partially luminescent and give off light for a brief period after exposure to another light.

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Stalactiteonground.jpg|Stalactite that fell thousands of years ago and is now in the midst of stalagmites

Caveofthemoundsstalagmite.jpg|A series of stalagmites growing on the ground in one of the display rooms

Cavecolumn.jpg|Several Stalactites hanging from the ceiling and a large column

Cave of the Mounds 1.jpg|Stalactites within Cave of the Mounds

Cave of the Mounds 2.jpg|Recess within Cave of the Mounds

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Ecosystem

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File:Leptothrix lichtmikroskopisch.jpg|Microscopic view of Leptothrix individuals

File:Gallionella ferruginea in Korrosionsprodukt.jpg|A large growth of Gallionella ferruginea bacteria.

File:Coecobrya phanthuratensis (10.3897-zookeys.824.31635) Figure 1 (cropped).jpg|A springtail in the Coecobrya genus, however it is a member of the species Coecobrya phanthuratensis, and not C. tenebricosa.

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Because the cave was underground before humans discovered it, animals like bats are not usually found in this subterranean environment. Despite this, a number of organisms that were small enough to seep through cracks in the ceiling populate the cave.

Footnotes

References

  • Cave of the Mounds website